There are conventional headlight control systems designed to control light distribution of a headlight of a vehicle to be controlled. Such headlight control systems aim at preventing dazzling of the driver of a preceding vehicle.
An example of such headlight control systems is disclosed in Japanese Patent Application Publication No. H06-270733. The headlight control system disclosed in the above-identified Patent Application Publication is installed in a vehicle to be controlled and is designed to control a light beam irradiated from each of paired headlights within a predetermined light-distribution range. The light-distribution range can be changed by adjusting a direction of the light beam irradiated from each headlight.
The headlight control system is equipped with an actuator having a shade member, such as a shade cam.
The shade member is fixed to a rotary shaft to be rotatable therewith by the actuator. The rotary shaft is disposed ahead of a headlamp of each headlight of the controlled vehicle and in the vehicle width direction. Rotation of the shade member together with the rotary shaft allows part of a light beam irradiated from the headlamp to be cut off. This allows a non-irradiated region to be formed within the light-distribution range.
The headlight control system is also equipped with a controller for controlling the actuator. The controller works to control a rotational position of the cam member through the actuator to thereby change the non-irradiated region depending on a measured distance between the controlled vehicle and a preceding vehicle. The change of the non-irradiated region depending on the measured distance between the controlled vehicle and the preceding vehicle prevents the light beam outputted from each headlight from being irradiated on the preceding vehicle.
The headlight control system however increases the difference in light-quantity (brightness) between an irradiated region and the non-irradiated region within the light-distribution range. This provides poor viewability of the non-irradiated region to the driver of the controlled vehicle, resulting in that it may be difficult for the driver of the controlled vehicle to visibly identity roadside objects located within the non-irradiated region, such as signboards.